Sea Otter 2011: FSA and BH's new 386 Evo bottom bracket standard

386 Evo will use the same cups as the currently available PressFit 30 system but in a wider shell measuring 86.5mm across.

(James Huang, Tech Editor)

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FSA will offer both K-Force and SL-K level road cranks in the new 386 Evo standard for now and unlike current BB30 models, both of these will also fit in conventional 68mm English threaded shells, too.

(James Huang, Tech Editor)

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The asymmetrical seat tube uses a squared-off profile.

(James Huang, Tech Editor)

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BH says the new Ultralight offers the best stiffness-to-weight ratio in the industry but still rides comfortably thanks to the slim seat stays, paper-thin tube walls, and skinny 27.2mm seatpost.

(James Huang, Tech Editor)

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Slotted housing stops are offset far enough from the tube that there's still room for plug-in barrel adjusters.

(James Huang, Tech Editor)

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BH's new Ultralight frame weighs just 747g for a painted 56cm size.

(James Huang, Tech Editor)

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The front end of BH's new Ultralight uses a 1 1/8"-to-1 1/2" head tube and a sub-300g all-carbon tapered fork.

Critics will no doubt lambast FSA and BH's decision to create yet another road bottom bracket 'standard' but the new 386 Evo system may actually make things easier. From an engineering perspective it's lighter and/or theoretically more rigid than many other systems, and perhaps most importantly, it's also compatible with other crank configurations.

In essence, 386 Evo is a 22mm-wider version of PressFit 30, using the same cups, straight 46mm bore and 30mm spindle diameter but in an 86.5mm-wide shell (BB30 measures 68mm across). 386 Evo gains the advantage of more widely spaced bearings than BB30, though, with virtually zero unsupported spindle on the matching 386 Evo-compatible cranks.

In addition, the larger diameter allows for lightweight aluminium spindles as compared to the steel pipes used for conventional external-cup cranks with 24mm axles. Spindle length is 15mm longer than on BB30. According to FSA, this means that ankle clearance is better than on conventional MegaExo external-cup cranksets (but not quite as good as BB30) and stance width remains unchanged.

Cross-compatibility is generous. While the system of course provides the most benefit with dedicated 386 Evo cranks and bottom bracket cups used in combination, 386 Evo cranks will fit in a conventional 68mm-wide threaded shell with the appropriate cups or BB30 shells with spacers. Alternatively, nearly any crank with a typical 24mm-diameter spindle will also fit into a 386 Evo bottom bracket shell, again when used with the appropriate cups – about the only cranks that won't fit in a 386 Evo shell are current BB30 or BBright models.

FSA's argument is that 386 Evo thus provides the larger and lighter spindle diameter of BB30 (with similar total crankset weights) but combined with the wider bearing spacing of BB86/BB90, all built into a symmetrical layout that's frame builder-friendly and won't force riders to adopt an entirely new system if they pick up a new chassis.

And from a frame builder's perspective, this larger interface provides heaps of surface area for adjoining tubes, making for an extra-wide down tube and seat tube similar to current BB90 (Trek Madone) and BB86 (Scott Addict, Giant TCR) fitments but also extra-tall chainstays and down tubes. Finally, 386 Evo only requires a properly sized straight tube in the shell so it's easier to manufacture than proper BB30 and can be made of lighter-weight carbon fiber.

FSA will offer two 386 Evo road cranks for now: the K-Force 386 Evo weighing just 654g and a slightly heavier SL-K version. BB30 cranks will continue on unabated but according to FSA general manager Matt Van Enkevort, what will eventually go away is the traditional MegaExo platform since 386 Evo will fit in those same shells. Still, the question remains: why introduce another bottom bracket system when there are already so many on the market?

"[386 Evo] takes what's good about BB30 and what's good for the frame and combines them into something that's better for both," says Van Enkevort. "People grumbled when 1-1/8in came out. I'm not saying that this is the same type of leap but it's similar – it brought something to the market that the others didn't. The only thing that's different here is that it's more compatible with other systems than any other crank we've made. As a manufacturer of components, that's what was so appealing for us."

BH's new Ultralight frame weighs just 747g for a painted 56cm size. Photo: James Huang

FSA developed 386 Evo in conjunction with Chris Cocalis of BH and not surprisingly, the new BH Ultralight takes full advantage of the new dimensions. Cocalis claims his new bike offers the best stiffness-to-weight ratio in the industry thanks to hugely oversized main tubes, giant chainstays and a tapered 1-1/8 to 1-1/2in front end but also a silky-smooth ride on account of the slim seatstays, paper-thin tube walls and skinny 27.2mm seatpost.

As compared to the current BH G5, Cocalis claims a 166 percent jump in torsional rigidity and a 125 percent improvement in rear-end stiffness. And yes, it's also ultra light, with a verified bare frame weight of 747g for a painted 56cm sample – about 100g lighter than a comparable G5. According to Cocalis, that same Ultralight frame weighs just 730g straight out of the mold, meaning there's just 17g of matte clear coat and decals used in the Spartan finish.

Other features include a forged 7075 aluminium derailleur hanger, a carbon fiber front derailleur braze-on tab, an all-carbon sub-300g fork with integrated crown race, slotted derailleur housing stops that are offset enough from the down tube that plug-in barrel adjusters will still fit, and a lifetime warranty with no rider weight limit.

Cocalis says production BH Ultralights will be available starting in July. US riders will be offered three to four complete bike variants while global buyers will most likely have three to four more additional ones to choose from. Framesets will be available for US$4,199. Other 386 Evo-compatible frames will soon be introduced by Litespeed and Wilier.

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